1. Field of the Invention
The invention relates to an internal combustion engine apparatus, a control method thereof, and a hybrid vehicle.
2. Description of the Related Art
An internal combustion engine device of this kind has been suggested that is provided with an engine of a direct injection system having attached thereto a unit for returning Exhaust Gas Recirculation (EGR) from an exhaust passage into an intake passage, wherein a base ignition timing is set on the basis of a fuel injection amount and a revolution speed of the engine, an actual EGR ratio is estimated by an intake pipe pressure and an intake air quantity, an ignition advance correction is set based on the estimated actual EGR ratio, and the base ignition timing is corrected by the ignition advance correction that has been set (see, for example, Japanese Patent Application Publication No. 11-201010 (JP-A-11-201010)). In this apparatus, the base ignition timing is corrected by ignition advance correction based on the actual EGR ratio, thereby making it possible to prevent a misfire and degradation of fuel consumption and exhaust gas even when the EGR amount varies in a transition state.
In the above-described apparatus, a misfire and degradation of fuel consumption and exhaust gas can be prevented even when the EGR amount varies in a transition state by correcting the base ignition timing by ignition advance correction based on the actual EGR ratio. However, when the actual EGR ratio varies, the estimation accuracy of the actual EGR ratio easily drops. Therefore, where the ignition timing is corrected by using the actual EGR ratio as is, the ignition timing can be advanced more than necessary and knocking can occur in the engine. Furthermore, an internal combustion engine apparatus that has the hardware configuration identical to that of the above-described internal combustion engine apparatus and in which the ignition timing is corrected based on a target EGR ratio as a target value of the EGR ratio, rather than on the actual EGR ratio, is also available. In this case, when the target EGR ratio varies, a difference appears between the target EGR ratio and the actual EGR ratio. Therefore, the ignition timing is not properly corrected and engine knocking can occur.